Gate valves which are used to control the flow of water through underground piping are buried in the ground. In order to operate the valves, a key is used to turn the operating nut of the valve. The key is mounted on the end of a long rod in order to reach the operating nut on the valve. Access to the operating nut is generally provided through a key box having a bonnet that is placed over the gate valve to prevent the operating nut from being buried in the ground. The bonnet is generally supported on wooden blocks located on each side of the gate valve. As a result of settling of the ground or deterioration of the block, the key box bonnet often shifts with respect to the gate valve allowing the ground to enter the bonnet and making it difficult to operate the operating nut.